Access method in communications systems with different service feature classes, and a corresponding communications system

ABSTRACT

The invention relates to a method for accessing subscriber terminals of different service feature classes on access channels of a communications system with different service feature classes, and relates to a corresponding communications system. According to the invention, at least two access channels (RACH 1 , RACH 2 ) of a different service feature class are provided in the communications system.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and hereby claims priority to PCTApplication No. PCT/DE01/02927 filed on 1 Aug. 2001 and GermanApplication No. 100 38 256.8 filed on 4 Aug. 2000, the contents of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a method for access fromsubscriber terminals in different service classes to access channels ina communications system having different service classes, and to acorrespondingly designed communications system.

[0003] Currently existing communications systems are being continuallyimproved and new, upgraded or optimized services are continuously beingprovided in these communications systems, and are expressed in differentservice classes in the corresponding communications systems. Servicessuch as these may represent specific services which a subscriber to thecommunications system can use directly, such as speech, data ormultimedia communication, or accompanying services such as a callanswering function or the like. However, it is also possible to provideservices which relate to the internal procedures in the communicationssystem, such as the nature, number and capacity of communicationschannels, the way in which data is passed on or processed, or the like.

[0004] WO 98/24250 A2 describes a communications system in which amobile station, which is referred to as VIP MS, has its own accesschannel, by which it receives exclusive access to special packet datachannels, as required.

[0005] One example of this is mobile radio systems, in whichsecond-generation mobile radio systems are currently operated, inparticular such as GSM or GPRS, and third-generation mobile radiosystems are specified, in particular such as UMTS or UTRAN. In thiscase, networks are also envisaged which form an interface functionbetween second- and third-generation mobile radio systems, in particularsuch as GERAN networks, and which thus have facilities which allowservices for the second generation and third generation of mobile radiosystems in parallel. In this case, the radio transmission part (radiointerface) of the GERAN network is designed on the basis of the secondgeneration of mobile radio systems, while the landline network part ofthe GERAN network is designed on the basis of the third generation ofmobile radio systems. A GERAN system thus supports not only the Ainterface for line-switched connections and the Gb interface forpacket-switched connections for the second generation, but also the lupsinterface for package-switched connections and the lucs interface forline-switched connections for the third generation.

[0006] By way of example, the provision of bidirectional communicationschannels is intended as a service in one of the first serviceclasses—corresponding to the second generation of mobile radiosystems—for GERAN networks of this type, that is to say channels in thedownlink direction from the communications system to a subscriberterminal and in the uplink direction from the subscriber terminal to thecommunications system, which channels are coupled to one another andhave a defined frequency separation (45 MHz) and a defined separation inthe time slot structure (3 time slots) for the TDMA radio interface forthe GERAN network. On the other hand, the service may also include as afurther service class unidirectional communications channels in theuplink direction or downlink direction, which are not coupled to anycorresponding second channel and thus allow greater flexibility forassignment of transmission capacities to communications connections.This makes it possible to make better use of the total availabletransmission capacities, allowing more communications connections to besupplied with the necessary transmission capacity than in the case ofsystems with bidirectional channels. These measures are described, byway of example, in Tdoc 2e00-126 “GERAN Physical Sub-Channels”, ETSISMG2 Working Session on EDGE, Seattle, Wash. USA, May 8-12, 2000.

[0007] Specifically, subscriber terminals can access communicationssystems via specific access channels. For example, a specific, commonsignaling channel (common control channel CCCH) is provided in mobileradio systems for this purpose, and is in the form of an access channel(random access channel RACH). However, previous access methods have notallowed a subscriber terminal to be assigned to the services in goodtime in that service class which is necessary or optimum for the serviceclass of that terminal overall or the service currently being requestedby the subscriber terminal. In fact, such optimized assignment iscarried out only in a second step after a previously complete access bythe subscriber terminal to the communications system, and this increasesthe signaling complexity or may even make it necessary for the terminalto access the communications system once again, on this occasionspecifically directed at the appropriate services in the appropriateservice class (directed retry).

SUMMARY OF THE INVENTION

[0008] One possible object of the present invention is therefore toprovide optimized access from subscriber terminals to a communicationssystem, making it possible to take into account the specific serviceclasses of the subscriber terminals, with as little complexity aspossible.

[0009] The method according to one aspect of the invention is used foraccess by subscriber terminals in different service classes to accesschannels in a communications system with different service classes.Provision is now made for at least two access channels with differentservice classes to be provided in the communications system. This meansthat any subscriber terminal can make contact, depending on its serviceclass or the service class of the currently requested service, withthose devices in the communications system which have the appropriateservice class, by accessing the appropriate access channel even duringthe first access to the communications system. This was impossible inprevious access methods, since only one access channel was provided inthe previously known systems, and this did not make it possible todistinguish between the service class of the subscriber terminals orbetween the services requested by them. The solution now makes theappropriate association with the appropriate service classes possible atthe earliest possible time.

[0010] In principle, the solution can be used in any type ofcommunications system which provides access from subscriber terminalsvia access channels and which provides different service classes.

[0011] Depending on the nature and number of service classes in thecommunications system, it is now possible for one access channel to beprovided for each service class in the communications system. However,certain service classes may also be combined to form a higher-levelservice class, for example individual services for a mobile radio systemmay be combined to form a service class which corresponds to thegeneration for these services or to the development stage (release)within one generation. This makes it possible to define in particularhigher and lower service classes, depending on the nature and thequality of the services contained in them.

[0012] Subscriber terminals in a higher service class, which cover boththe services in this higher service class and the services in a lowerservice class, can either access the communications system basically viathe appropriate access channel of the higher service class, or else theycan make this access dependent on the currently requested service. Ifthis service can be handled alternatively or even better via theservices in the lower service class, then the subscriber terminal in asituation such as this can access the access channel of the appropriatelower service class, in order to keep the services in the higher serviceclass free for those subscriber terminals whose services can be handledonly in this way. It is sensible to allow only access to one accesschannel in the lower service class for subscriber terminals in the lowerservice class.

[0013] As already described, in a situation such as this, specificservices in a second-generation mobile radio system may be provided asthe first service class, while specific services in a third-generationmobile radio system can be provided as the second service class.Alternatively, however, the service classes may also represent servicesat different development levels (release) of mobile radio systems withinone generation of mobile radio networks.

[0014] In the case of a GERAN network as described above, by way ofexample, bidirectional transmission channels may thus be provided as afirst service class, with unidirectional transmission channels beingprovided as the second service class, and with a first access channelbeing provided in a bidirectional transmission channel, and a secondaccess channel being provided in a unidirectional transmission channel.Depending on the capability to process bidirectional or unidirectionaltransmission channels, the subscriber terminal can then access theappropriate access channel for it, and can thus initiate access to thecommunications system. The further connection to the communicationssystem can then be made automatically in the appropriate service class,which is intrinsically defined by the nature of the access.

[0015] The two access channels may be inserted in various suitablemanners into the structure of the transmission channels or of thephysical carries of the communications system. The transmission channelfor the second access channel may thus be provided on the same physicalcarrier as the transmission channel for the first access channel, or thetransmission channel for the second access channel may be provided on adifferent physical carrier than the transmission channel for the firstaccess channel.

[0016] The inventors also propose a communications system which hasdevices for different service classes for setting up communicationsconnections to subscriber terminals in different service classes.Devices are now provided for assignment of at least two access channelsfor the subscriber terminals. As already described above, the subscriberterminals can be allocated in an objective manner to the service classesin the communications system in a simple manner and at a very early timevia these separate access channels.

[0017] Specifically, the communications system may be in the form of amobile radio system and may have first devices for the second generationof mobile radio systems as well as second devices for the thirdgeneration of mobile radio systems. One such mobile radio system wouldbe a GERAN network, as has already been described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other objects and advantages of the present inventionwill become more apparent and more readily appreciated from thefollowing description of the preferred embodiments, taken in conjunctionwith the accompanying drawings of which:

[0019]FIG. 1 shows a schematic illustration of the access to a GERANnetwork;

[0020]FIG. 2 shows a schematic illustration of the channel structure oftwo access channels within a bidirectional communications channel; and

[0021]FIG. 3 shows a schematic illustration of the channel structure ofthe unidirectional access channel within a unidirectional communicationschannel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to likeelements throughout.

[0023]FIG. 1 shows a schematic illustration of a mobile radio systemwhich is intended to be used as a specific example of a communicationssystem which operates according to the described method. The mobileradio system illustrated here essentially comprises a GERAN networkwhich is used as an interface to a central network (core network) whichon the one hand may be designed on the basis of one of thesecond-generation mobile radio system standards (GSM), and on the otherhand may also be designed on the basis of one of the third-generationmobile radio system standards (UMTS). The aim here is to consider thesituation in which the core network provides not only services for thesecond-generation mobile radio system but also for the third-generationmobile radio system, so that the GERAN network is configuredappropriately to provide these services as well. The GERAN network isthus designed firstly to provide services for a service class of thesecond generation of mobile radio systems, and secondly to provideservices for a service class for the third generation of mobile radiosystems.

[0024] For this purpose, the GERAN network is connected to the corenetwork firstly via interfaces for the second generation (A interfacefor line-switched connections and Gb interface for packet-switchedconnections) and secondly via interfaces for the third generation (lucsinterface for line-switched connections and lups interface forpacket-switched connections). No final decision has yet been made onwhether the lucs interface will actually be used in GERAN networks. Thisinterface is therefore annotated by the note ffs (for further study) inFIG. 1. The GERAN network contains base station controllers BSC, whichare connected to one another via an lur′ interface and are connected tobase stations (base transceiver stations) BTS1, BTS2 which, as theactual transmitting and receiving devices, produce the connection tosubscriber terminals MS1, MS2.

[0025] At the subscriber terminal end, in this case in the form ofmobile subscriber terminals MS1, MS2, the GERAN network has a radiointerface Um which is designed essentially on the TDMA principle for thesecond generation of mobile radio systems but which, in addition to theservices for the second generation, can likewise offer services for thethird generation in order to create an effective connection between thesubscriber terminals MS1, MS2 and the appropriate interfaces to the corenetwork. The subscriber terminals MS1, MS2 may likewise have differentservice classes, which correspond to services for the second or thirdgeneration of mobile radio systems. In particular, it is assumed herethat the subscriber terminal MS1 is designed such that it can processnot only bidirectional communications connections such as those inprevious mobile radio systems for the second generation, but alsounidirectional communications connections such as those proposed forthird-generation mobile radio systems. In contrast, the subscriberterminal MS2 is assumed to be designed such that it can process onlybidirectional communications connections.

[0026] At the radio interface Um end of the GERAN network, two accesschannels RACH1, RACH2 are now provided for the subscriber terminals MS1,MS2 with the different service classes, rather than only one accesschannel RACH as in the past. In this case, the first access channelRACH1 is provided for a service in a lower service class, namely for abidirectional communications connection. In contrast, the second accesschannel RACH2 is provided for a service in a higher service class,namely for a unidirectional communications connection. Thesecond-generation subscriber terminals MS1, which can likewise beassociated with this lower service class, can thus access only the firstaccess channel RACH1 while, in contrast, the third-generation subscriberterminals MS2 can access either the first access channel RACH1 or elsethe second access channel RACH2. In this case, it has not yet beendefined when and under what conditions the third-generation subscriberterminals MS2 will access which of the access channels RACH1, RACH2.This may be defined in any suitable manner. The definition canadvantageously be made controlled by signaling in a common signalingchannel in the downlink direction (downlink DL), the broadcast controlchannel BCCH. This means that the BCCH will contain the instruction forthe subscriber terminals MS2 as to whether, for example, they shouldgenerally have access to the communications system on a specific accesschannel RACH1, RACH2 of the two access channels RACH1, RACH2, or whetherthey should have access to a specific access channel RACH1, RACH2, forexample the unidirectional channel RACH2, in order to provide specificservices, and should otherwise always access the other access channelRACH1, which in this case represents the standard access channel. Theother subscriber terminals MS1 in the lower service class would receive(via the signaling channel BCCH) only the signaling to always access theaccess channel RACH1.

[0027] As illustrated in FIG. 2, the first access channel RACH1 islocated in the first time slot tsO in a time slot frame TF on thatcarrier in the uplink direction UL which forms a pair with the BCCHcarrier in the downlink direction DL. There, the BCCH is likewiselocated in the first time slot ts0 of a time slot frame TF. Thefrequencies of the two carriers are separated from one another by acertain frequency separation, which differs depending on the nature ofthe mobile radio system and on the frequency bands used there. In mobileradio systems which operate in accordance with a GSM 900 standard, thatis to say for transmissions in the 900 MHz band, the frequencyseparation is 45 MHz, as illustrated in FIG. 2. The time slot schemesare offset by three time slots ts with respect to one another in time,so that the first time slot ts0 in a time slot frame TF in the downlinkdirection DL of the BCCH carrier is offset by three time slots withrespect to the first time slot ts0 of the RACH carrier in the uplinkdirection UL.

[0028] As shown in FIG. 2, the second access channel RACH2 may now beprovided on the same carrier in the uplink direction UL as the firstaccess channel RACH1, but in different time slots.

[0029]FIG. 3 shows an alternative way to insert the second accesschannel RACH2 into the structure of the transmission channels. Here, thesecond access channel RACH2 is provided on a separate, purelyunidirectional carrier in the uplink direction UL.

[0030] The method and apparatus thus make it possible in a simple mannerto distinguish between subscriber terminals in different service classesby accessing access channels for different service classes, in thepresent specific example in particular by using the different capabilityof subscriber terminals MS1, MS2 to process bidirectional orunidirectional communications connections.

[0031] The invention has been described in detail with particularreference to preferred embodiments thereof and examples, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention.

1. A method for requesting communications connections which areassociated with transmission channels for different service classes in acommunications system, with transmission channels for a first serviceclass being bidirectional transmission channels, and transmissionchannels for a second service class being unidirectional transmissionchannels, in which an individual access channel (RACH1, RACH2) is usedfor each of the two service classes in order to request communicationsconnections which are associated with transmission channels for the twoservice classes.
 2. The method as claimed in claim 1, characterized inthat a subscriber terminal optionally uses one of the two accesschannels.
 3. The method as claimed in claim 1, characterized in that asubscriber terminal exclusively uses one of the two access channels. 4.The method as claimed in one of claims 1 to 3, characterized in that oneaccess channel (RACH1, RACH2) is provided for each service class oftransmission channels.
 5. The method as claimed in one of claims 1 to 4,characterized in that a first lower service class and a second higherservice class are provided, and access to an access channel for thelower service class (RACH1) is provided for first subscriber terminalsand access to an access channel for the lower service class (RACH1) orto an access channel for the higher service class (RACH2) is providedfor second subscriber terminals, depending on the nature of the servicethat is currently required by the subscriber terminal.
 6. The method asclaimed in claim 5, characterized in that services for asecond-generation mobile radio system are provided as the first serviceclass, and services for a third-generation mobile radio system areprovided as the second service class.
 7. The method as claimed in claim5, characterized in that services at different development levels withinone generation of mobile radio systems are provided as service classes.8. The method as claimed in one of claims 1 to 7, characterized in thatthe transmission channel for the second access channel (RACH2) isprovided on the same physical carrier as the transmission channel forthe first access channel (RACH1).
 9. The method as claimed in one ofclaims 1 to 7, characterized in that the transmission channel for thesecond access channel (RACH2) is provided on a different physicalcarrier than the transmission channel for the first access channel(RACH1).
 10. A communications system, having devices for processingrequests for communications connections which are associated withtransmission channels for different service classes, with communicationsconnections being set up in a bidirectional transmission channel intransmission channels for a first service class, and communicationsconnections being set up in a unidirectional transmission channel intransmission channels for a second service class, and in which thedevices for processing a request for communications connections whichare associated with transmission channels for the two service classeseach provide one individual access channel (RACH1, RACH2) for each ofthe two service classes.
 11. The communications system as claimed inclaim 10, characterized in that the communications system is in the formof a mobile radio system and has first devices in the second generationof mobile radio systems as well as second devices in the thirdgeneration of mobile radio systems.
 12. A subscriber terminal, having adevice for requesting communications connections which are associatedwith transmission channels for different service classes in acommunications system, with transmission channels for a first serviceclass being bidirectional transmission channels and transmissionchannels for a second service class being unidirectional transmissionchannels, in which the device for requesting communications connectionswhich are associated with transmission channels for the two serviceclasses uses in each case one individual access channel (RACH1, RACH2)for each of the two service classes.